The scene occurred on Thursday evening in the historic centre of Grasse, in the Alpes-Maritimes.
The mother of a family was at her home when she heard screams coming from outside.
She then passed her head through the window and saw that his son was assaulted by three men.
The mom then grabbed a knife and went down to the bottom of his building, before stabbing one of the attackers.
This man, major, was taken in charge by the fire department, and his days are not in danger.
As to the mother of the family, she was placed in police custody.